1. Field of the Invention
The present invention relates to a writing stem for writing instruments, having, for example, a grip section comprising an elastic material.
2. Description of the Related Art
Known examples of writing instruments of this kind include a finger gripping device, disclosed for instance in U.S. Pat. No. 4,601,598, incorporated by reference in its entirety. The gripping device described therein is formed as a barrel made of a flexible material, on whose surface a plurality of circular ribs are formed.
However, since such a rib of a grip according to the conventional structure has little level difference between the crests and grooves of its ribs, and is mainly intended to achieve a cushion effect with the flexibility of its flexible material (e.g., the flexible composition of the material itself), no sufficient cushion effect can be achieved, resulting in fatigue of a user""s thumb and fingers.
The present invention is directed to solving this problem and others found in the conventional structure, and an object thereof is to provide a writing stem for writing instruments having a proper and sufficient cushion effect for a user""s gripping thumb and fingers.
In order to attain the above-described object and others, according to the invention, there is provided a writing stem for writing instruments, having a grip section including an elastic material, with a plurality of protruding pieces formed on the surface of the grip section that can be bent by a gripping force. The bending of the protruding pieces can provide the user with a cushioned effect (e.g., a xe2x80x9csoft feelxe2x80x9d). Since only the portions of the writing stem where the user""s thumb and fingers actually come into contact therewith are compressed, the user""s grip will be comfortable and non-fatiguing.
Optionally, it is possible to form clusters of the plurality of protruding pieces on the surface of the grip section including a portion positioned substantially approximately 30 to 40 mm behind the tip of the writing instrument, and the length of these clusters in the axial direction can be made equivalent to about ⅔ of the overall length of the grip section in the axial direction. By forming these clusters of the plurality of protruding pieces over a length equivalent to about ⅔ of the overall length of the grip section in the axial direction, a cushion effect and a non-slip effect can be achieved on and around the portion with which the user""s thumb and fingers actually come into contact, resulting in a writing stem which causes the user to feel no excessive softness but a proper degree of firmness. Thus, the user is not fatigued even after continuous writing for many hours. The clusters on the grip section may be unified to cover the section all around. However, more preferably, three such clusters may be provided in the circumferential direction separately from one another, which correspond to the user""s thumb and the fingers (e.g., the index finger and the middle finger) gripping the stem.
Optionally, it is also possible to vary the height of the plurality of protruding pieces at regular spatial intervals, to vary the depth of grooves between adjacent protruding pieces at regular spatial intervals, to vary the thickness of the plurality of protruding pieces at regular spatial intervals, or to vary the spacing between adjacent protruding pieces at regular spatial intervals. Since it is thereby made possible to vary a degree of bending ease of the plurality of protruding pieces by use of a regular spatial period, portions where the protruding pieces are difficult to bend are formed at regular intervals. Thus, a writing stem is formed which causes the user to feel no excessive softness but a proper degree of firmness, and does not fatigue the user even after continuous writing for many hours.
Optionally, it is also possible to gradually increase the height of the plurality of protruding pieces from the forward end and from the rearward end of the writing stem to an intermediate portion in the axial direction of the grip section, so that the height of the plurality of protruding pieces is the highest at the intermediate portion. This makes the portion other than the intermediate portion, which is unlikely to be gripped by the user, difficult to bend, and the intermediate portion which is likely to be gripped by the user, easy to bend, and enables the user to grip the intermediate portion whose relative hardness is most preferable for the user, resulting in a writing stem which does not fatigue the user even after continuous writing for many hours.